Homeostasis

Question 1

What is Homeostasis?

Answer 1

The maintenance of a constant ‘internal environment’.

Question 2

What is the Hypothalamus?

Answer 2

The Hypothalamus is at the base of the brain and it is the thermoregulatory centre of the body.

Question 3

How does the body detect changes in temperature?

Answer 3

Temperature receptors in the skin detect changes in the external temperature. They pass this information to the processing centre in the brain, called the hypothalamus. The hypothalamus also has temperature receptors to detect changes in the temperature of the blood.

Question 4

What are 3 ways the skin can help DECREASE the body’s temperature?

Answer 4

1. Sweat can be secreted by sweat glands. This works as the body uses it’s heat to evaporate the sweat.
2. Heat radiation can be increased by vasodilation. This is when blood vessels dilate so they are nearer the surface of the skin.
3. convection can be increased by hairs lying flat. This happens when the hair erector muscles relax.

Question 5

What are 3 ways the skin can help INCREASE the body’s temperature?

Answer 5

1. Sweat glands will not secrete sweat
2. Radiation is reduces by vasoconstriction. This is when blood vessels will contract so that blood is shunted away from the skin.
3. Convection can be reduced by standing hairs up. This happens when the hair erector muscles contract and it is effective as it traps a layer of still air.

Question 6

What is the stimulus in homeostasis?

Answer 6

Any change or deviation from the ideal level.

Question 7

What is meant by negative feedback?

Answer 7

When the corrective action that has been established, is switched off as the ideal level has been reached.

Question 8

How are glucose levels in the blood DECREASED with homeostasis?

Answer 8

If too much glucose enters the blood from the small intestine, then:
The pancreas secretes INSULIN which converts the glucose in to glycogen in the liver, where it is stored for later use.

Question 9

How are glucose levels in the blood INCREASED with homeostasis?

Answer 9

If there is too little glucose in the blood (e.g. After exercise) then the pancreas will secrete GLUCAGON which converts the glycogen in the liver into glucose.

Question 10

What is glucose?

Answer 10

A soluble carbohydrate needed for cellular respiration

Question 11

What is diabetes?

Answer 11

A condition where the pancreas cannot produce insulin to control levels of glucose in the blood.

Question 12

What is glucagon

Answer 12

A hormone which make the liver break down glycogen into glucose.

Question 13

What is glycogen?

Answer 13

An insoluble form of glucose that is stored in the liver.

Question 14

What is insulin?

Answer 14

A hormone made in the pancreas that causes glucose to pass from the blood and be stored as glycogen in the liver’s cells.

Question 15

What are hormones?

Answer 15

Chemical messengers carried in the blood that cause changes in the body.

Question 16

What is hypo-glycemia?

Answer 16

A condition where you have dangerously low levels of glucose in your blood.

Question 17

Where does glucose enter the blood?

Answer 17

Small intestine.

Question 18

Why and how is carbon dioxide maintained at a certain level in the body?

Answer 18

Carbon dioxide is a toxic waste product of respiration that alters the pH levels (bad for enzymes).
It is excreted by lungs when exhaling.

Question 19

Why and how is urea maintained at a certain level in the body?

Answer 19

Urea is a toxic waste product of liver breaking down excess amino acids.
It is removed when filtered from the blood by the kidneys, before being passed to the bladder and excreted in urine.

Question 20

Why and how is water maintained at a certain level in the body?

Answer 20

Water is needed at a certain level so that the body’s cells do not burst or shrivel.
Water is lost in many ways: breathing out (water vapour), sweating and in urine via kidneys. Water is gained by drinking.

Question 21

Why and how is sugar maintained at a certain level in the body?

Answer 21

Sugar is needed for respiration in cells.

It is reduced by insulin and increased with glucagon.

Question 22

Why and how is temperature maintained at a certain level in the body?

Answer 22

Temperature is needed so enzymes work at their optimum but don’t denature at >45 degrees.
(Regulation explained in better detail elsewhere)

Question 23

Why and how is ions maintained at a certain level in the body?

Answer 23

Ions are needed so cells function at their optimum and they don’t loose/gain too much water by osmosis.
Ions are lost by sweating and in urine. They are gained by eating and drinking.